Over two days, the participants, ranging in age from 6 to 15, have been racking their brains for etymology, Latin roots, memory tricks, and grammar-school spelling lessons (“I” before “E” except after “C”?) trying to recall the spelling for words as obscure as “chiaroscurist” (an artist specializing in the interplay of light and dark) or “autochthonous” (indigenous or endemic to a particular region).

A record audience is expected to tune in to ESPN to watch the live broadcast of the final round at 8 p.m. Eastern Time Thursday, including many former contestants who say this is the time of year that gets spelling fanatics excited.

“It’s definitely one of the most exciting things I’ve done with my life, I mean, it sounds silly, it’s just a spelling bee, but the intensity, the pressure, and after winning, going on talk shows, it was a surreal experience,” says Kerry Close, who, at age 13, spelled “Ursprache” (a language reconstructed from evidence of later languages) correctly to win the 2006 championship.

Unlike some contestants, Ms. Close, now a sophomore at Cornell University and an aspiring journalist in New Jersey, says she put in relatively little preparation for each of the five years she participated: an hour a day and then reading through an entire dictionary the final year in which she won. She says her penchant for spelling hasn’t done much for her Scrabble game, but the experience of devoting so much time and concentration as a teenager toward a specific goal was invaluable.

“Plus it’s a cool thing you can talk about for the rest of your life,” she says.

Most bee aficionados consider the Scripps bee the Super Bowl of spelling competitions, so many get excited this time of year and follow the rounds, trying to keep up, says Ned Andrews, who was 13 when he spelled “antediluvian” correctly to win the championship in 1994. Now a public defender in Portsmouth, Va., Mr. Andrews later wrote a guidebook for students looking to prepare for the big leagues.

“The image of someone just poring over a dictionary for hours on end is incorrect,” he says, “instead of just staring off into space at the breakfast table, pay attention to the words around you. Read the back of the cereal box, but actually pay attention to the words, squeeze everything you can from what you’re already doing.”

The competition, which started off Wednesday with a preliminary, computerized round, ran through two more rounds Thursday before the elimination semi-final and final.

While most participants this year were between the ages of 12 and 14, Lori Anne Madison was this year’s outlier: The 6-year-old from Lake Ridge, Va., was the youngest participant in the bee’s history and – with a precociously outsized personality – attracted an outsized portion of the media’s attention.

Ms. Madison, who correctly spelled “dirigible” (a type of blimp) before being tripped up in Round 3 on the word “ingluvies” (a part of a bird’s anatomy), told reporters earlier that previous competitors didn’t know how easy they had it.

“The words were much easier back then, someone won on ‘therapy,’ ” she said giggling. “I could’ve won in those times, double time, but now they’ve made them much harder.”

It took Wendy Guey Lai four years of competing before she won in 1996 by spelling “vivsepulture” (the act of burying someone alive) correctly. She says her father, a Taiwanese immigrant, was a lifelong student of the English language, and she regularly read his English grammar books as she prepared for competitions.

“I learned to stop viewing it only as a competition. It’s a process, my dad would say, that it’s not about whether you win or not,” says Ms. Lai, now a math teacher in the Boston public schools. “It’s about all this knowledge that you gain in the process: the process that you engage in to prepare for a competition. You try to develop yourself to the fullest, learn as much as you can, learning that as a young kid is so important, that it’s not the end result that’s important, but the journey there.”

Lai’s spelling prowess hasn’t improved her Scrabble game either, though she says it has made her hyperaware of misspelling or mispronouncing words, like sherbert instead of sherbet, or libary instead of library.

“You definitely want to correct people on it, but then you think, hmm, is it worth it? I don’t want to be super aggravating, but it is something that I’ll notice,” she says.

According to contest organizers, words topping lists of favorites for this year’s participants include cwm, (a Welsh word for valley), serendipity (the faculty or phenomenon of finding valuable or agreeable things not sought for), as well as humuhumunukunukuapuaa.

The winner receives $30,000, a $2,500 US savings bond, a Nook reader, reference books from Encyclopedia Britannica, and other awards.